As its name suggests, PetroChina Company Ltd is the listed arm of state-owned China National Petroleum Corporation (CNPC). It is China's biggest oil producer, and is listed in Hong Kong, New York, and Shanghai.

Wison Engineering Services, a supplier to PetroChina, said mainland authorities had taken company records and temporarily frozen some of its bank accounts amid a widening probe into the giant oil producer and its parent, China National Petroleum Corp.

Wison also said it was no longer able to contact its chairman and founder, Hua Bangsong, who the company has said was assisting the authorities in the investigation. In a statement, Wison said Zhao Hongbin, the manager of the finance department of the company’s unit, Wison Engineering, was also assisting in the investigation. Wison said it was not aware of the nature of the probe.

In a separate filing with the Hong Kong stock exchange, the company said its executive director and chief financial officer, Chen Wenfeng, had resigned from his post to pursue other business opportunities.

Last night, the firm said Jojo Choy Sze-chung had resigned as a director and chairman of the audit committee.

The authorities have taken books and records and frozen certain bank accounts

WISON ENGINEERING SERVICES

“As part of their investigations, the regulatory authorities made enquiries about certain projects of the group, have taken books and records and frozen certain bank accounts of the group,” the company said in the statement. “The company was not told the reason for freezing our bank accounts.

“After the company’s communication with the regulatory authorities, some of the frozen bank accounts have been released.”

Shares in Shanghai-based Wison – which has derived most of its revenue from PetroChina in recent years – have been suspended in Hong Kong since early this month, when the company first said Hua was helping the authorities.

The stock last traded at HK$1.98. It had fallen 30 per cent after the central government announced the investigation into several former top executives at PetroChina and CNPC late last month.

According to Wison’s filings with the stock exchange, Hua founded the company in 1997 and built it into the country’s largest private petrochemical contractor, thanks largely to revenue from PetroChina, one of the world’s most valuable energy firms, with a market capitalisation of about US$240 billion.

This article appeared in the South China Morning Post print edition as Wison records seized as probe widens